Compositions for polishing or planarizing substrates comprising a metal, metal oxide, or metal composite are well known in the art. Such compositions typically contain an abrasive material in an aqueous solution and are known as polishing slurries. The polishing slurries usually are applied to a surface of the substrate by contacting the surface with a polishing pad saturated with the slurry composition. Typical abrasive materials include silicon dioxide, cerium oxide, aluminum oxide, zirconium oxide, and tin oxide. U.S. Pat. No. 5,527,423, for example, describes a method for chemically-mechanically polishing a metal layer by contacting the surface with a polishing slurry comprising metal oxide particles in an aqueous medium.
Conventional polishing compositions sometimes are not entirely satisfactory at polishing or planarizing substrates comprising metals, metal oxides, or metal composites. In particular, the abrasive material of the polishing slurry can adhere to the substrate being polished or planarized, such that abrasive material remains on the surface of the substrate following polishing and subsequent cleaning. The use of such polishing slurries in chemical-mechanical polishing can result in poor surface quality due to the leftover slurry deposits. Since the performance of a substrate is directly associated with the planarity of its surface and absence of particulate deposits, it is important to use a polishing composition that leaves a high quality polish with minimal residual slurry particles on the surface of the substrate.
There remains a need for a method of polishing or planarizing a substrate that exhibits a desirable polishing or planarization efficiency, uniformity, and removal rate but minimizes or avoids residual abrasive material being left on the substrate following polishing or planarization. The present invention seeks to provide such a method. These and other advantages of the present invention will be apparent from the description of the invention provided herein.